Problem: $ { {-5} \times \left[\begin{array}{rr}{3} & {-2} \\ {-1} & {-2} \\ {3} & {-1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-5}\times{3} & {-5}\times{-2} \\ {-5}\times{-1} & {-5}\times{-2} \\ {-5}\times{3} & {-5}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-15} & {10} \\ {5} & {10} \\ {-15} & {5}\end{array}\right]}$